This invention relates to endless flexible belt conveyors and more particularly to troughing conveyers for receiving and carrying granular or shiftable materials.
Troughing conveyers are used in mining and quarry operations for receiving sand, gravel, rock, coal and such loose pourable, shiftable material. Troughing conveyers are also used for handling and carrying granular material such as grain, beans and the like which have a tendency to slump or spread due to vibrations during movement on conveyor belting.
Due to the tendency of such material to flow, spread and shift by gravity in the course of movement, it has become conventional to provide intermediate sets of idler rollers in conveyor systems to support side edges of the flexible conveyor belting in a canted or angular condition so as to form a trough lengthwise the load-carrying reach of such belting. A typical arrangement of idler rollers for a troughing conveyor is shown in U.S. Pat. No. 2,743,810 which issued to Armstrong, May 1, 1956. The Armstrong patent discloses the use of spirally-grooved rollers for tending to center the belting as a trough for conveying loose granular material. The jist of the invention in the Armstrong patent resides in providing hollow walled idler rollers mainly for absorbing the impact or shock from the material falling onto the belting. So far as the tracking is concerned, Armstrong relies solely on the spiral grooving and rubber belting for good tracking. This however, assumes that the load remains centered in the troughing conveyor and fails to account for the shifting or tendency for the granular material to gravitate toward one or the other slanted edges of the belt. Such shift of the load causes greater weight and traction between the belt and rollers on the loaded side and release of tracking action on the unloaded side of the belting.